It is well known that manifest thyroid dysfunction causes mood disorders. In the literature there are few studies related with subclinical thyroid dysfunction and anxiety. We aimed to determine if there exists a relation between the anxiety and subclinical thyroid dysfunction. This study was carried out in the Meram Medical Faculty of Selçuk University, Department of Endocrinology and Metabolism. Eighty-five outpatients were enrolled into the study. In the presence of normal fT(3) and fT(4), patients were grouped as subclinical hyperthyroid with TSH lower than 0.1 mU/L (n = 24), subclinical hypothyroid with TSH higher than 4.5 mU/L (n = 32) and euthyroid subjects (n = 29). Beck's Anxiety Inventory (BAI) was administered to all patients. There was no any statistically significant difference between euthyroid and study groups in terms of age, gender, weight and height (p<0.05). One-way ANOVA showed that both of the subclinical hypothyroid and subclinical hyperthyroid groups had significantly higher anxiety scores than euthyroid group (F: 11.4, p<0.001). Manifest hypothyroidism and hyperthyroidism, as causes of mental and neurological dysfunction have been known for a long time, but the relation between subclinical thyroid dysfunction and anxiety is less well studied. We have found that subclinical thyroid dysfunction increases the anxiety of patients whether hyperthyroid or hypothyroid. Overlap of symptoms common to both thyroid dysfunction and anxiety is an important limitation in this study. Mood changes especially anxiety due to subclinical thyroid dysfunction may have an important impact on the patient's quality of life. Negative effect on quality of life may be an indication of treatment in these patients. It is the first study evaluating anxiety in subclinical hypothyroidism in the literature.